Transport across the membrane

Question 1

Why can’t all cells travel across the membrane?

Answer 1

Because of the Phospholipid bilayer, creates a non-polar zone (hydrophobic) with it’s tails (in the middle).

Question 2

Which molecules can pass freely through the membrane?

Answer 2

Very small polar molecules.

Hydrophobic molecules.

Question 3

Which molecules cannot pass through the membrane?

Answer 3

Charged molecules.

Large Hydrophilic molecules.

Question 4

Active Transport

Answer 4

Needs energy to pass, ATP.
Creates a concentration gradient. 
From high to low (except endo-exo)
1. Protein pumps
2. Co-Transport
3. Endo-Exo- Cytosis

Question 5

Passive Transport

Answer 5

Does not need energy.
Primary force is random movement of molecules. No control over movement.
Wants Equilibrium,equal concentration.
High to Low.
1. Diffusion
2. Osmosis
3. Facilitated Diffusion

Question 6

Diffusion

Answer 6

Random movement of particles of a solute from an area of higher concentration to an are of lower concentration.
Stops at equilibrium.
Equal movements of particles in both directions, no net movement.
Very small molecules: O2, CO2,NH3.
Hydrophobic molecules: Steroids.
Non-Polar: Fatty Acids

Question 7

Osmosis

Answer 7

Water H2O moves where there is greater amount of solute, until the solute concentration on both sides is equal.
Solute cannot cross the membrane.

Question 8

Facilitated Diffusion

Answer 8

Diffusion of specific particles through transport proteins found in the membrane.
Stops at equilibrium.
Ions, Glucose, Amino Acids.
Channels: Constitutively open.
Ligand-gated= open in response to chemical signal.
Voltage-gated= Change in membrane electrical potential.
Mechanically gated= Mechanical stress, pressure, distortion.
Carrier Proteins:
Glut 1= Glucose transporter.

Question 9

Protein Pumps

Answer 9

Primary active transport.
Energy: ATP hydrolysis.
Creates a concentration gradient.
Ions.
Sodium (Na+) Potassium (K+) pump:
Takes 3 Na+
Uses ATP(keeps Phosphate, ADP gone)
Releases Na+ (outside)
Takes 2 K+ (from outside)
Releases Phosphate to open from the inside and release K+ on the inside.

Question 10

Co-Transport

Answer 10

Secondary active transport.
2 molecules move together.
1 moves from from high to low concentration (passive transport), releases energy.
1 moves from low to high concentration (active transport).
Can move in same direction or opposite.
Ions, Glucose, Amino Acids.

Question 11

Endo- Exo- Cytosis

Answer 11

Uses vesicles, cell membrane bulges inward until release.
Bulk transport. 
Nothing to do with concentration.
Large molecules, proteins, lipoproteins, viruses, bacteria, lots of small molecules, hormones.
Endo: Take molecules into the cell.
- Pinocytosis
- Phagocytosis
- Receptor mediate endocytosis
Exo: Take molecules out of the cell.
- Constitutive exocytosis
- Regulated exocytosis